Energy storage is an important technology for the future of the energy infrastructure, and it is one of the top challenges in the energy industry today. Inexpensive, large-scale, and efficient energy storage is an enabling technology for exploiting intermittent renewable energy sources such as solar energy, wind energy, etc. Improvements in energy storage systems will allow renewable energy sources to comprise a more significant fraction of the national energy grid. Energy storage can be used to smooth out fluctuations in renewable energy generation, reducing or eliminating intermittency and replacing unpredictable energy with manageable, dispatchable energy. For example, energy storage systems may convert electric energy into another mode of storable energy, such as mechanical, potential, chemical, biological, electrical, or thermal energy, and then convert the stored energy back into electric energy when the energy is deployed. Energy storage devices are generally categorized by their performance characteristics and the applications they serve.
Various technologies for energy storage are known. Energy storage devices may be used to bridge the timing gap between energy production and user energy requirements. Solutions for efficient energy storage have gained increasing interest due to the emphasis on the development of alternative energy resources, such as solar electric energy, solar thermal energy, wind energy, and the like. Such alternative energy resources often are only available intermittently. Exemplary technologies for energy storage include high-power flywheels, superconducting magnetic energy storage, high-power super-capacitors, various advanced battery technologies including flow batteries, pumped storage hydroelectric, thermal energy storage, and compressed air energy storage. According to recent studies, compressed air energy storage holds particular promise as an economical technology for bulk energy management.
Compressed air energy storage (CAES) is known to be an effective way to store energy, but it is currently not efficient and not cost-effective. The existing state of the art of CAES is focused on advanced adiabatic methods (AA-CAES) and isothermal methods (I-CAES). However, to date such systems have not been found to provide a competitive alternative for energy storage. However, conventional CAES systems are based on storing energy at high pressure. Energy storage systems wherein the main energy storage is in the compressed air have disadvantages, including high costs associated with compressing to high pressures, energy losses associated with the compressive heating, and the cooling on expansion.
A new hybrid option for energy storage is disclosed and referred to herein as Low-Cost Hybrid Energy Storage System (LCHESS). LCHESS brings down the cost of energy storage while increasing the efficiency of these systems. The LCHESS system combines high-temperature thermal energy storage (HTES) with low pressure compressed air energy storage. A compressor-turbine (reducer/expander) turbocharger augments the air flow from the compressed air reservoir, and the combined flow is heated to high temperatures in the HTES system. The disclosed hybrid system optimizes energy storage between thermal energy storage and compressed air storage.